1. Field of the Invention
The present invention relates to apparatus for separating and washing clay, shale, and other contaminants from gravel, and particularly to a log washer having staggered paddles.
2. Description of the Related Art
Gravel is a commonly used material in the construction industry, being used in concrete, in paving, in landscaping, and as a component in other materials and the performance of other functions. Gravel may be obtained by strip mining techniques, from quarries, by dredging operations, and other methods. Typically gravel obtained by such methods will be mixed with clay mud balls or other soils, often containing grass, roots, and small wood or tree branch fragments, or with shale, sand, sandstone, limestone, or other earthen materials. In order to prepare gravel for market, it is necessary to separate the gravel from the earthen materials in which it is found, and to wash the gravel so that it is free from such contaminants.
Fine grades of gravel are usually separated and washed in devices which use a screw conveyor or auger, having a continuous, smooth, helical spiral blade about its circumference similar to the thread of a screw. Examples of such devices are shown in U.S. Pat. No. 1,695,021, issued Dec. 11, 1928 to Puryear (two parallel screws driven by planetary gears, with improved arrangement of water jets and valves for directing the flow of water in the tank), and in U.S. Pat. No. 2,025,841, issued Dec. 31, 1935 to Young (trough with screw conveyors and a novel de-shaling hopper for removing shale from gravel by water jets). Sometimes notches will be cut into the threads at regular intervals to break up clumped material, e.g., the cut-flight conveyor shown in FIG. 31 at page 1426 of Marks"" Mechanical Engineers"" Handbook (4th ed., 1941), U.S. Pat. No. 4,448,678, issued May 15, 1984 to Gentry (lignite separator with a single, hybrid shaft having a spiral lower end and a notched upper end).
Coarse gravel is usually separated and washed using log washers. Typical log washers have a water tank or trough mounted at an inclined angle relative to horizontal, with a pair of parallel shafts or logs mounted bearings in the end walls of the trough so that they are free to rotate. A motor is connected to one end of the shafts by appropriate gearing to drive the shafts to rotate in opposite directions. Each shaft has a plurality of paddles or blades mounted thereon, usually mounted to the shaft at an angle, the paddles on adjacent shafts being staggered so that mud balls and other clumps of material broken down by grinding between the blades of adjacent shafts, and so that the shafts carry solid rock and gravel material towards the raised end of the shaft, where the separated and washed gravel is discharged to an appropriate hopper or conveyor belt. Typically, in a conventional log washer, the paddles on a single shaft are mounted in long rows at equally spaced angular distances about the axis of the shaft, e.g., at 90xc2x0 intervals.
Examples of conventional log washers with proposed improvements are disclosed in U.S. Pat. No. 1,609,652, issued Dec. 7, 1926 to McQueen (log washer with improved method of attaching the paddles to the shaft using keyways and aligned slots), and U.S. Pat. No. 3,807,558, issued Apr. 30, 1974 to Hamm (gravel separator using both sand screw and log washer where material introduced to trough lateral to screw or log washers into high velocity stream of water). U.S. Pat. No. 2,336,991, issued Dec. 14, 1943 to Leveke, shows a gravel washer with a single shaft having multiple sections of different diameters, one section being square in section, in which the sections are mounted eccentrically relative to the bearing to produce greater agitation in the trough.
The problem with conventional log washers is that the paddles on each shaft are mounted in straight rows. This configuration means that each time a row of paddles completes a revolution, the load in the tank of trough will be thrown or shifted laterally against the sidewalls of the tank. The lateral shifting of the load in the tank creates agitation and vibration along the entire length of the tank, at least four times per revolution in the case of log washers having four rows of paddles. The vibrations cause rocking in the tank supports, requiring that more time and effort be expended in preparing the foundation or supports for the tank or trough, and potentially result in greater wear and stress being placed on the bearings and/or the shaft. The present invention is directed towards a log washer shaft having staggered sections of paddles along each row, in order to reduce load shifting stresses, resulting in less strain and stress being placed upon the tank supports.
Other forms of separators are known for separating other mixtures of solids, having structures less related to the present invention, such as those described in the following patents: U.S. Pat. No. 1,972,195, issued Sep. 4, 1934 to Lacy, Jr. (ore washer with a chain and sprocket with buckets mounted on the chain to scoop material in a trough); U.S. Pat. No. 2,050,458, issued Aug. 11, 1936 to Ovestrud et al. (portable separator with a scrubber and a screen, but no log washers); U.S. Pat. No. 2,324,549, issued Jul. 20, 1943 to P. L. Wigton (separator with a spiral ribbon mounted on a shaft where the shaft is supported by a chain or belt); U.S. Pat. No. 2,489,161, issued Nov. 22, 1949 to Scholes (endless belt separator with improved seals); U.S. Pat. No. 4,234,415, issued Nov. 18, 1980 to de Tuya Casuso (ore separator with rotating drum); U.S. Pat. No. 5,868,256, issued Feb. 9, 1999 to Teppo (clay refiner with rotating drum); and International Patent No. WO 97/16253, published May 9, 1997 (rotating drum with inner and outer chambers).
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a log washer with staggered paddles solving the aforementioned problems is desired.
The log washer with staggered paddles is a device for washing and separating aggregates, such as sand, gravel, ores, etc., from clay, dirt, organic waste matter, and other impurities. The log washer has a water tank or trough having one end inclined or raised relative to horizontal. A pair of shafts are mounted for rotation in bearings in the end walls of the tank, and connected to a driver by appropriate gearing so that the shafts rotate in opposite directions. Each shaft has a plurality of paddles mounted thereon, each paddle being mounted at an angle to the shaft to raise washed aggregates up the inclined trough to a discharge hopper or conveyor belt. Further, the paddles on each shaft are grouped in sections, the radial angle formed by adjacent sections with the shaft being staggered, the paddles on adjacent shafts being offset so that the aggregate material is ground between the paddles.
The adjacent sections of paddles on each shaft are separated by transition zones characterized by an absence of paddles. The transition zones provide for enhanced scrubbing of the aggregate material.
Accordingly, it is a principal object of the invention to reduce the vibration in a log washer caused by shifting loads through staggering sections of paddles on the log washer shafts.
It is another object of the invention to relieve stress and strain on the supports of a log washer tank by staggering sections of paddles on the log washer shafts.
It is a further object of the invention to provide a log washer which separates aggregates from waste materials and washes the aggregate having smoother operation through staggering shifting loads in the log washer water tank.
Still another object of the invention is to reduce wear and tear on log washer tank supports, log washer shafts, and shaft bearings by offsetting sections of paddles in each row of log washer paddles.
It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.